1. Field of the Invention
The present invention relates to a magnetic recording element, and a magnetic recording device using that. For example, the present invention relates to a magnetic recording element, in which spin-polarized electrons flow to control the spin direction of a magnetic material, and which records data.
2. Description of the Related Art
In recent years, information recording devices have been used to support or promote the wide-ranging highly information-oriented society, because such devices satisfy various requirements such as mass capacity, high speed, durability and low cost. Moreover, it is desired to provide a technique of enhancing the foregoing features. Magnetic recording devices using the magnetic moment of a ferromagnetic material have been widely used as hard disk drives, for example. Recently, a magnetic recording device has been proposed to be used as a magnetoresistive random access memory (MRAM) having both high speed and non-volatility.
However, according to the requirements of recent high density, scale-down from 100 nanometers to several tens of nanometers or less is required in a unit cell storing one-bit data. For this reason, a technical barrier is appearing in the method of writing data. More specifically, according to electromagnetic field writing used for the foregoing hard disk drive and MRAM, the amount of current for generating a magnetic field required for write increases with a reduction of the memory cell size. In addition, a problem such as crosstalk to neighboring cells inevitably arises.
Recently, the direct current-driven magnetization switching is verified by the document, F. J. Albert et al., Appl. Phys. Lett. Vol. 77, pp. 3809-3811 Dec. 4, 2000. It is expected that the phenomenon will provide new writing capable of solving the problem in the foregoing current magnetic field writing.
The foregoing phenomenon is as follows. That is, when a conduction electron spin-polarized in a direction different from the magnetization direction (spin direction) of a magnetic material passes through the magnetic material, spin angular momentum of the conduction electron acts on and is transferred to the magnetization of the magnetic material to generate a torque to switch the magnetization direction of the magnetic material. Use of the phenomenon can achieve a more direct influence on the nanoscale magnetic material than the magnetization switching by electro-magnetic field and decrease current required for write with a reduction of the cell size.
However, there is the following problem so far. In order to switch the magnetization direction directly by a current, an extremely large current such as 10 mA to several mA is required when the cell size is about 100 nm to several tens of nanometers. Namely, efficiency of the direct current-driven magnetization switching must be enhanced in order to prevent device breakdown and exothermic reaction, and further to achieve low power consumption. In other words, there is a need to switch the magnetization direction by as small a current as possible.